As well as animal bones and fragments of Hanseatic pottery, they found a nail from a medieval ship, along with a more recent wreck.

Courtney Nimura, from the Museum of London, was among the experts invited to Lynn by the West Norfolk and King’s Lynn Archaeological Society.

“It’s really interesting, I’d never been to Norfolk before,” said Dr Nimura. “People are immensely proudd of their maritime heritage in this town and rightly so. There’s a lot of history to be learnt.”

Dr Clive Bond, from the archaeological society, said the group had covered the area from Common Staithe Quay to the Nar Loop.

Animal bones were among the more common finds. Dr Bond said centuries ago cattle would have been butchered near the waterfront, with unwanted cuts such as the heads thrown in the river.

The Nar Loop - once part of a more extensive river frontage and home to shipbuilding and the Lynn whaling fleet - is now an expanse of mud and reed, where a number of hulks have been left to rot.

Dr Simon Draper, from the Nautical Archaeology Society, said they had pieced together the hitstory of one vessel, called the Jo-Al.

“She came from Brittany, she was built in 1955,” he said. “She came to the UK in 1978 and went to Paignton, then to Newlyn, then to king’s Lynn, where she sank at the quayside.”

Dr Draper said the vessel’s hull had areas of sheathing where it had been patched up from earlier mishaps.

Poring over the finds at Marriott’s Warehouse, finds specialist Sue Anderson said: “What you’ve got is a mixture opf lots of different bits. You’ve got some from the 15th and 16th centuries going right through to the 18th Century.

“Most of this is locally-produced pottery, but there’s some German imports.”

One fragment, featuring part of a face, matched the design of a medieval Hanseatic beer or wine bottle.

A nail used to secure planks to clinker-built boats was also found near the Custom House.